Chemical mechanical polishing composition containing composite silica particles, method of making the silica composite particles and method of polishing a substrate

ABSTRACT

A chemical mechanical polishing composition includes water, colloidal silica abrasive particles with a silica core containing a nitrogen species, a cerium compound coating including cerium oxide, cerium hydroxide or mixtures thereof, and a positive zeta potential, optionally an oxidizing agent, optionally a pH adjusting agent, optionally a biocide and optionally a surfactant. The chemical mechanical polishing composition has a pH of less than 7. Also described is a method of polishing a substrate containing silicon dioxide and a method of making the composite colloidal silica particles with the coating of cerium oxide, cerium hydroxide or mixtures thereof. The chemical mechanical polishing composition can be used to enhance the removal of silicon dioxide from a substrate in an acid environment.

FIELD OF THE INVENTION

The present invention is directed to a chemical mechanical polishingcomposition containing composite silica particles, method of making thecomposite silica particles and method of polishing a substrate. Morespecifically, the present invention is directed to a chemical mechanicalpolishing composition containing composite silica particles, method ofmaking the composite silica particles and method of polishing asubstrate, wherein the composite silica particles comprise a silicacore, a nitrogen species, a cerium compound coating comprising ceriumoxide, cerium hydroxide or mixtures thereof on the silica core, apositive zeta potential and an acid pH.

BACKGROUND OF THE INVENTION

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting and dielectric materialsare deposited on or removed from a surface of a semiconductor wafer.Thin layers of conducting, semiconducting, and dielectric materials canbe deposited by several deposition techniques. Common depositiontechniques in modern processing include physical vapor deposition (PVD),also known as sputtering, chemical vapor deposition (CVD),plasma-enhanced chemical vapor deposition (PECVD), and electrochemicalplating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the wafer becomes non-planar. Because subsequentsemiconductor processing (e.g., metallization) requires the wafer tohave a flat surface, the wafer needs to be planarized. Chemicalmechanical planarization, or chemical mechanical polishing (CMP), is acommon technique used to planarize substrates, such as semiconductorwafers. In conventional CMP, a wafer is mounted on a carrier assemblyand positioned in contact with a polishing pad in a CMP apparatus. Thecarrier assembly provides a controllable pressure to the wafer, pressingit against the polishing pad. The pad is moved (e.g., rotated) relativeto the wafer by an external driving force. Simultaneously therewith, apolishing composition (“slurry”) or other polishing solution is providedbetween the wafer and the polishing pad. Thus, the wafer surface ispolished and made planar by the chemical and mechanical action of thepad surface and slurry.

Abrasives are the primary components of chemical mechanical polishingslurries. Silica and ceria nanoparticles are two of the most commoncompositions. Silica particles are widely used in chemical mechanicalpolishing because of their availability and long history in glasspolishing. More importantly, the use of positively charged silica atacidic pH ranges has enabled an enhanced oxide removal rate at lowsilica wt %. However, their polishing removal rate and selectivities areoften inadequate in ILD and STI processes. Accordingly, there is a needto provide an improved silica for enabling enhanced silicon dioxideremoval rate at acid pH.

SUMMARY OF THE INVENTION

The present invention provides a chemical mechanical polishingcomposition, comprising:

water;

colloidal silica abrasive particles comprising a silica core comprisinga nitrogen species, a cerium compound coating comprising cerium oxide,cerium hydroxide or mixtures thereof on the silica core, and a positivezeta potential;

optionally an oxidizing agent;

optionally a pH adjusting agent;

optionally a biocide;

optionally a surfactant; and

a pH less than 7.

The present invention further includes a method of making compositecolloidal silica abrasive particles providing:

a chemical mechanical polishing composition comprising:

water;

colloidal silica abrasive particles comprising a nitrogen containingspecies and a positive zeta potential;

0.0001 wt % to 1 wt % of a source of cerium ions; and

an oxidizing agent;

optionally a biocide;

optionally a surfactant;

adding an alkaline pH adjusting agent to the chemical mechanicalpolishing composition to provide a pH of greater than 7;

optionally applying heat at temperatures of greater than or equal to 35°C.; and

adjusting the pH of the chemical mechanical polishing composition toless than 7 with an acid pH adjusting agent to form colloidal compositesilica particles comprising a silica core comprising a nitrogen species,a cerium compound comprising cerium oxide, cerium hydroxide or mixturesthereof coating the silica core, and a positive zeta potential.

The present invention also provides a method for chemical mechanicalpolishing of a substrate, comprising:

providing a substrate, wherein the substrate comprises silicon dioxide;

providing a chemical mechanical polishing composition comprising:

water;

colloidal silica abrasive particles comprising a silica core comprisinga nitrogen species, a cerium compound coating comprising cerium oxide,cerium hydroxide or mixtures thereof on the silica core, and a positivezeta potential;

optionally an oxidizing agent;

optionally a pH adjusting agent;

optionally a biocide;

optionally a surfactant; and

a pH less than 7;

providing a chemical mechanical polishing pad with a polishing surface;

-   -   creating dynamic contact at an interface between the polishing        surface of the chemical mechanical polishing pad and the        substrate with a down force of 0.69 to 34.5 kPa; and    -   dispensing the chemical mechanical polishing composition onto        the chemical mechanical polishing pad at or near the interface        between the chemical mechanical polishing pad and the substrate;        and wherein the substrate is polished and some of the silicon        dioxide is polished away.

The chemical mechanical polishing composition and method of the presentinvention enable enhanced silicon dioxide removal rates at an acid pH.

DETAILED DESCRIPTION OF THE INVENTION

As used throughout this specification the following abbreviations havethe following meanings, unless the context indicates otherwise: °C.=degrees Centigrade; mL=milliliters; μ=μm=microns; kPa=kilopascal;Å=angstroms; mm=millimeters; nm=nanometers; min=minute; rpm=revolutionsper minute; lbs=pounds; kg=kilograms; wt %=percent by weight; RR=removalrate; ZP=zeta potential; mv=millivolts; Si=silicon; Si₃N₄=siliconnitride; DEAMS=(N,N-diethylaminomethyl) triethoxysilane, 98% (GelestInc., Morrisville, Pa.); TMOS=tetramethyl orthosilicate;TMAH=tetramethyl ammonium hydroxide; TEA=tetraethyl ammonium; andEDA=ethylenediamine; EOPA=3-ethoxypropylamine; Ti=titanium; TiN=titaniumnitride; W=tungsten; PS=Polishing Slurry of the Invention;CS=Comparative Polishing Slurry.

The term “chemical mechanical polishing” or “CMP” refers to a processwhere a substrate is polished by means of chemical and mechanical forcesalone and is distinguished from electrochemical-mechanical polishing(ECMP) where an electric bias is applied to the substrate. The term“TEOS” means the silicon oxide formed from the decomposition oftetraethyl orthosilicate (Si(OC₂H₅)₄). The term “composition” and“slurry” are used interchangeably through-out the specification. Theterms “a” and “an” refer to both the singular and the plural. Allpercentages are by weight, unless otherwise noted. All numerical rangesare inclusive and combinable in any order, except where it is logicalthat such numerical ranges are constrained to add up to 100%.

The chemical mechanical polishing composition and method of the presentinvention is useful for polishing a substrate comprising silicondioxide. The chemical mechanical polishing composition of the presentinvention comprises (preferably consists of) water, colloidal silicaabrasive particles containing a silica core, a nitrogen species, acerium compound coating comprising cerium oxide, cerium hydroxide ormixtures thereof on the silica core, and a positive zeta potential,optionally an oxidizing agent, optionally a biocide, optionally asurfactant, optionally a pH adjusting agent, and a pH less than 7.Preferably, the cerium compound coating on the silica core consists of acerium compound selected from the group consisting of cerium oxide,cerium hydroxide and mixtures thereof. More preferably, the ceriumcompound coating on the silica core of the colloidal silica particles iscerium hydroxide. The silica core comprising a nitrogen species andhaving a net positive zeta potential wherein the silica core is coatedwith the cerium compound comprising cerium oxide, cerium hydroxide ormixtures thereof forms the composite colloidal silica particles of thepresent invention.

The water contained in the chemical mechanical polishing composition ofthe present invention is preferably at least one of deionized anddistilled to limit incidental impurities.

The chemical mechanical polishing composition of the present inventioncontains 0.1 wt % to 40 wt % colloidal silica abrasive particlescontaining a silica core, a nitrogen species, a cerium compound coatingcomprising cerium oxide, cerium hydroxide or mixtures thereof on thesilica core and a net positive zeta potential, preferably, 1 wt % to 25wt % colloidal silica abrasive particles containing a silica core, anitrogen species, a cerium compound coating comprising cerium oxide,cerium hydroxide or mixtures thereof on the silica core, and a netpositive zeta potential, more preferably, 1 wt % to 20 wt %, mostpreferably, 10 wt % to 20 wt %. The colloidal silica abrasive particlescontaining a silica core, a nitrogen species and a cerium compoundcoating on the core and a net positive zeta potential, preferably, havean average particle size of <100 nm, more preferably, 50 to 90 nm, mostpreferably, 60 to 80 nm, as measured by dynamic light scatteringtechniques (DLS).

In the chemical mechanical polishing compositions of the presentinvention, the chemical mechanical polishing compositions provided,contain colloidal silica abrasive particles having a positive zetapotential, wherein the colloidal silica abrasive particles comprise anitrogen containing species from a nitrogen-containing compound. Suchnitrogen-containing compounds can be incorporated within the colloidalsilica abrasive particles, or can be incorporated on a surface of thecolloidal silica abrasive particles, or the chemical mechanicalpolishing compositions of the present invention can contain, as initialcomponents, colloidal silica abrasive particles having a combination,wherein the nitrogen-containing compounds are incorporated within thecolloidal silica abrasive particles having the positive zeta potential,and, wherein, the nitrogen-containing compounds are incorporated on asurface of the colloidal silica abrasive particles.

Colloidal silica abrasive particles comprising nitrogen-containingcompounds are commercially available, or can be prepared by those ofordinary skill in the art as described in the chemical and colloidalsilica abrasive particle literature. An example of commerciallyavailable colloidal silica particles comprising nitrogen-containingcompounds of FUSO™ BS-3 colloidal silica (containing EOPA) (FusoChemical Co., Ltd., Osaka, Japan). Such colloidal silica abrasiveparticles are preferably prepared by the Stober process, well known tothose of ordinary skill in the art.

The colloidal silica abrasive particles having a positive zeta potentialof the present invention comprise (on a surface of colloidal silicaabrasive particles, within colloidal silica abrasive particles, orcombinations thereof) nitrogen-containing compounds which include, butare not limited to, ammonium compounds having a general formula:R¹R²R³R⁴N⁺  (I)wherein R¹, R², R³ and R⁴ are independently chosen from hydrogen,(C₁-C₆)alkyl, (C₇-C₁₂) arylalkyl and (C₆-C₁₀)aryl. Such groups can besubstituted with one or more hydroxyl groups. Such colloidal silicaabrasives containing ammonium compounds can be prepared from methodsknown in the art or in the literature.

Examples of such nitrogen-containing ammonium compounds aretetramethylammonium, tetraethylammonium, tetrapropylammonium,tetrabutylammonium, tetrapentylammonium, ethtyltrimethylammonium anddiethyldimethylammonium.

Nitrogen-containing compounds can also include, but are not limited to,compounds having an amino group such as a primary amine, a secondaryamine, a tertiary amine or a quaternary amine. Such nitrogen-containingcompounds can also include an amino acid having from one to eight carbonatoms such as lysine, glutamine, glycine, iminodiacetic acid, alanine,valine, leucine, isoleucine, serine and threonine.

In various embodiments, a weight ratio of the chemical species to silicain the colloidal silica abrasive particles of the present invention ispreferably from 0.1 wt % to 10 wt %.

Optionally, but preferably, aminosilane compounds are incorporated onsurfaces or into colloidal silica abrasive particles of the chemicalmechanical polishing compositions of the present invention. Suchaminosilane compounds include, but are not limited to, primaryaminosilanes, secondary aminosilanes, tertiary aminosilanes, quaternaryaminosilanes and multi-podal (e.g., dipodal) aminosilanes. Theaminosilane compound can include substantially any suitable aminosilane.Examples of aminosilanes which can be used to practice the presentinvention are bis(2-hydroxyethyl)-3-aminopropyl trialkoxysilane,diethylaminomethyltrialkoxysilane,(N,N-diethyl-3-aminopropyl)trialkoxysilane),3-(N-styrylmethyl-2-aminoethylaminopropyl tiralkoxysilane), aminopropyltrialkoxysilane, (2-N-benzylaminoethyl)-3-aminopropyl trialkoxysilane),trialkoxysilyl propyl-N, N, N-trimethyl ammonium,N-(trialkoxysilylyethyl)benzyl-N,N,N-trimethyl ammonium,(bis(methyldialkoxysiylylpropyl)-N-methyl amine,bis(trialkoxysilylpropyl)urea,bis(3-(triakoxysilyl)propyl)-ethylenediamine,bis(trialkoxysilylpropyl)amine, bis(trialkoxysilylpropyl)amine,3-aminopropyltrialkoxysilane,N-(2-aminoethyl)-3-aminopropylmethyldialkoxysilane,N-(2-aminoethyl)-3-aminopropyltrialkoxysilane,3-aminopropylmethyldialkoxysilane, 3-aminopropyltrialkoxysilane,3-aminopropyltriethoxysilane, (N-trialkoxysilylpropyl)polyethyleneimine,trialkoxysilylpropoyldiethylentriamine,N-phenyl-3-aminopropyltrialkoxysilane,N-(vinylbenzyl)-2-aminoethyl-3-aminopropyltrialkoxysilane,4-aminobutyl-trialkoxysilane, (N,N-diethylaminomethyl) triethoxysilane,and mixtures thereof. Those of ordinary skill in the art readilyappreciate that aminosilane compounds are commonly hydrolyzed (orpartially hydrolyzed) in an aqueous medium. Thus, by reciting anaminosilane compound, it is understood that the aminosilane or ahydrolyzed (or partially hydrolyzed) species or condensed speciesthereof can be incorporated in the colloidal silica abrasive particles.

In various embodiments, a weight ratio of the aminosilane species tosilica in the colloidal silica abrasive particles is preferably from 0.1wt % to 10 wt %, more preferably, from 0.25 wt % to 9 wt %, even morepreferably, from 0.5 wt % to 5 wt %.

Colloidal silica abrasive particles which include nitrogen containingcompounds incorporated within the colloidal silica abrasive particlesare preferably prepared by the Stober process, wherein organicalkoxysilanes, such as TMOS and TEOS are used as precursors for silicasynthesis and nitrogen-containing compounds are used as catalysts. TheTMOS and TEOS as precursors undergo hydrolysis and condensation in anaqueous alkaline environment. The catalysts used to maintain an alkalinepH are nitrogen-containing species, such as, but are not limited to,ammonia, TMAH, TEA, EOPA and EDA. As counterions, thesenitrogen-containing compounds are inevitably trapped inside thecolloidal silica abrasive particles during particle growth, thusresulting in colloidal silica abrasive particles comprisingnitrogen-containing compounds internally incorporated within thecolloidal silica abrasive particles. Examples of a commerciallyavailable colloidal silica abrasive particles which includenitrogen-containing compounds incorporated within the particles areparticles available from FUSO™, such as FUSO BS-3™ colloidal silicaabrasive particles.

The colloidal silica particles of the present invention containing thenitrogen species and the positive zeta potential comprises a ceriumcompound coating comprising cerium oxide, cerium hydroxide or mixturesthereof on the core of the composite colloidal silica particles.Preferably, the cerium compound is selected from the group consisting ofcerium oxide, cerium hydroxide and mixtures thereof. Most preferably,the cerium coating on the silica core of the composite silica particlesis cerium hydroxide. Sources of cerium which provide the cerium ions(cerium (III) and cerium (IV)) for forming the cerium compound coatingon the core of the silica particles include, but are not limited tocerium acetate, cerium nitrate, cerium sulfate, cerium chloride, ceriumfluoride, cerium bromide, cerium iodide, cerium oxide, ceric ammoniumnitrate, ammonium cerium sulfate, cerium hydrate or mixtures thereof.

Sources of cerium ions are included in the chemical mechanical polishingcompositions in amounts of 0.0001 wt % to 1 wt %, preferably, from 0.001wt % to 0.5 wt %, more preferably, from 0.01 wt % to 0.005 wt %, mostpreferably, from 0.01 wt % to 0.002 wt %.

Optionally, the chemical mechanical polishing compositions providedcontain a pH adjusting agent. Such pH adjusting agents include inorganicand carboxylic acids. Inorganic acids include, but are not limited tonitric acid, sulfuric acid, phosphoric acid, or mixtures thereof.Carboxylic acids include monocarboxylic acids and dicarboxylic acids.Monocarboxylic acids include, but are not limited to acetic acid,propionic acid, butyric acid, benzoic acid, or mixtures thereof.Dicarboxylic acids include, but are not limited to malonic acid, oxalicacid, succinic acid, adipic acid, maleic acid, malic acid, glutaricacid, tartaric acid, salts thereof or mixtures thereof. More preferably,the acid chemical mechanical polishing compositions provided contain adicarboxylic acid, wherein the dicarboxylic acid is selected from thegroup consisting of malonic acid, oxalic acid, succinic acid, tartaricacid, salts thereof and mixtures thereof. Still more preferably, theacid chemical mechanical polishing compositions provided contain adicarboxylic acid, wherein the dicarboxylic acid is selected from thegroup consisting of malonic acid, oxalic acid, succinic acid, saltsthereof and mixtures thereof. Most preferably, the acid chemicalmechanical polishing compositions provided contain the dicarboxylic acidsuccinic acid or salts thereof. Such dicarboxylic acids are included inthe chemical mechanical polishing compositions to maintain a desiredacid pH.

Alkaline compounds which can be used to adjust the pH of the chemicalmechanical polishing composition include, but are not limited toammonia, ammonium hydroxide, potassium hydroxide, sodium hydroxide ormixtures thereof. Such alkaline compounds are included in the chemicalmechanical polishing compositions of the present invention in amounts tomaintain a desired pH. In general, such alkaline compounds are used tomaintain an initial alkaline pH during preparation of the compositecolloidal silica particles as described below.

The chemical mechanical polishing compositions used in the chemicalmechanical polishing methods of the present invention have a final pH ofless than 7, preferably 2 to 6.5, more preferably, 3 to 6, mostpreferably, 4 to 5. A most preferred pH adjusting agent to maintain thechemical mechanical polishing composition at the desired acid pH rangeis succinic acid.

Optionally, but preferably, the chemical mechanical polishingcompositions of the present invention include an oxidizing agent.Oxidizing agents include, but are not limited to, hydrogen peroxide,monopersulfate, iodates, magnesium perphthalate, peracetic acid, andother per-acids, persulfate, bromates, perbromate, persulfate, peraceticacid, periodate, nitrates, hypochlorites and mixtures thereof.Preferably, the oxidizing agent is selected from the group consisting ofhydrogen peroxide, perchlorate, perbromate, periodate, persulfate andper acetic acid. More preferably, the oxidizing agent is hydrogenperoxide.

Preferably, the chemical mechanical polishing composition providedcontains 0.0001 wt % to 0.1 wt %, more preferably, 0.001 wt % to 0.05 wt%, even more preferably, 0.0025 wt % to 0.01 wt % of an oxidizing agent.

Optionally, the chemical mechanical polishing compositions can containbiocides, such as KORDEX™ MLX (9.5-9.9% methyl-4-isothiazolin-3-one,89.1-89.5% water and ≤1.0% related reaction product) or KATHON™ ICP IIIcontaining active ingredients of 2-methyl-4-isothiazolin-3-one and5-chloro-2-methyl-4-isothiazolin-3-one, each manufactured by The DowChemical Company, (KATHON™ and KORDEX™ are trademarks of The DowChemical Company). Such biocides can be included in the acid chemicalmechanical polishing compositions of the present invention inconventional amounts, as known to those of ordinary skill in the art.

Optionally, the chemical mechanical polishing composition of the presentinvention includes a surfactant. Such surfactants include but are notlimited to non-ionic surfactants such as esters, ethylene oxides,alcohols, ethoxylates, silicon compounds, fluorine compounds, ether,glycosides and their derivatives. Surfactants can also includeconventional cationic surfactants.

Surfactants can be included in the chemical mechanical polishingcompositions in conventional amounts, such as, but not limited to, of0.001 wt % to 0.1 wt %, preferably, 0.001 wt % to 0.05 wt %, morepreferably, 0.01 wt % to 0.05 wt %, still more preferably, 0.01 wt % to0.025 wt %.

The present invention further comprises a method of making the colloidalcomposite silica particles by providing a chemical mechanical polishingcomposition comprising (preferably consists of) water, colloidal silicaabrasive particles comprising a nitrogen species and having a positivezeta potential, 0.0001 wt % to 1 wt % of a source of cerium ions andtheir counter anions, an oxidizing agent, optionally a biocide,optionally a surfactant, and a pH adjusting agent to initially providean alkaline pH of greater than 7, then followed by a pH adjusting agentto provide a final acid pH.

Preferably, the alkaline pH is 7.5 or greater, more preferably thealkaline pH is from 8 to 12, even more preferably, the alkaline pH isfrom 8 to 11, most preferably, the alkaline pH is from 8 to 9. The finalacid pH is less than 7, preferably 2 to 6.5, more preferably, 3 to 6,most preferably, 4 to 5.

The pH adjusting agents are described above. A most preferred alkalinepH adjusting agent is ammonia. A most preferred pH adjusting agent tomaintain the chemical mechanical polishing composition at the desiredacid pH range is succinic acid.

Preferably, the colloidal silica particles of the present inventioncontaining the nitrogen species are prepared by a one-pot wet process.The cerium compound coating is prepared by a nucleation,condensation-polymerization, or similar process in aqueous media. Thisis in contrast to any dry process techniques where a calcining processis typically used to try and anneal cerium oxide from ceria-containingprecursors to achieve the crystallinity that is desired, e.g. fumed orpyrogenic ceria. One-pot means the wet-process ceria is formedhomogeneously with silica core particle without forming precipitates orphase separation and without requiring the subsequent particleseparation and re-dispersion steps.

Preferably, the method of making the colloidal abrasive silica particlesof the present invention is by a one-pot wet process by the addition ofan oxidizing agent, preferably, hydrogen peroxide, and a source ofcerium ions. The mixture is homogenous and the color is observed asred-brownish. The pH is thereafter adjusted to an alkaline range with apH adjusting agent such as ammonia, ammonium hydroxide, or anotheralkaline pH agent described above, before aging at elevated temperaturefor a desired amount of time, as described below. After cooling to roomtemperature, the slurry appeared to be light yellowish. The slurry isthen titrated down to targeted acidic pH for chemical mechanicalapplication. Optionally, the silica particles of the present inventioncan be treated with aminosilane compounds using conventional processeswell known in the art prior to application of the oxidizing agent. Theprocess provides the formation of stable colloidal abrasive silicaparticles of the present invention.

Including an oxidizing agent in the chemical mechanical polishingcomposition of the present invention with sources of cerium ions asdisclosed above enables the formation of colloidal silica particles ofthe present invention, wherein the silica particles comprising thenitrogen species and a positive zeta potential have a silica core with acoating comprising cerium oxide, cerium hydroxide, or mixtures thereof.The oxidizing agents of the present invention are disclosed above. Mostpreferably, the oxidizing agent for forming the cerium compound coatedsilica particles comprising the nitrogen species and the positive zetapotential of the present invention is hydrogen peroxide.

Optionally, but preferably, the chemical mechanical polishingcomposition comprising the colloidal silica abrasive particles of thepresent invention comprising a silica core with a nitrogen species,positive zeta potential and cerium compound coating can be prepared byheating the chemical mechanical polishing composition at temperatures of35° C. or greater, preferably, from 35° C. to 80° C., more preferably,from 40° C. to 60° C., even more preferably, from 45° C. to 55° C.

Preferably, when the chemical mechanical polishing composition isheated, heating or aging is done for 6 hours to 336 hours, morepreferably, from 6 hours to 168 hours, even more preferably, from 6hours to 24 hours, most preferably, from 6 hours to 12 hours.

The method of making the chemical mechanical polishing composition ofthe present invention also includes providing a chemical mechanicalpolishing composition comprising (preferably consists of) water,colloidal silica abrasive particles comprising a nitrogen species, apositive zeta potential, 0.001 wt % to 1 wt % of a source of cerium ionsand their counter anions, an oxidizing agent, optionally a biocide,optionally a surfactant, and a pH adjusting agent; providing an alkalinepH adjusting agent to add to the chemical mechanical polishingcomposition to provide a pH of greater than 7; then heating the chemicalmechanical polishing composition at temperatures from 35° C. or greater,preferably, from 35° C. to 80° C., more preferably, from 40° C. to 60°C., even more preferably, from 45° C. to 55° C.; and adding a pHadjusting agent to the chemical mechanical polishing composition tolower the pH below 7 to provide colloidal silica abrasive particlescomprising a silica core comprising a nitrogen species, a ceriumcompound coating comprising cerium oxide, cerium hydroxide or mixturesthereof on the silica particle core and a net positive zeta potential.

The substrate polished in the chemical mechanical polishing method ofthe present invention comprises silicon dioxide. The silicon dioxide inthe substrate includes, but is not limited to, tetraethyl orthosilicate(TEOS), borophosphosilicate glass (BPSG), plasma etched tetraethyl orthosilicate (PETEOS), thermal oxide, undoped silicate glass, high densityplasma (HDP) oxide.

Optionally, the substrate polished in the chemical mechanical polishingmethod of the present invention further comprises silicon nitride. Thesilicon nitride in the substrate, if present, includes, but is notlimited to, silicon nitride material, such as, Si₃N₄.

Optionally, the substrate polished in the chemical mechanical polishingmethod of the present invention also comprises Ti, TiN, W orcombinations thereof.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing pad provided can be anysuitable polishing pad known in the art. One of ordinary skill in theart knows to select an appropriate chemical mechanical polishing pad foruse in the method of the present invention. More preferably, in themethod of polishing a substrate of the present invention, the chemicalmechanical polishing pad provided is selected from woven and non-wovenpolishing pads. Still more preferably, in the method of polishing asubstrate of the present invention, the chemical mechanical polishingpad provided comprises a polyurethane polishing layer. Most preferably,in the method of polishing a substrate of the present invention, thechemical mechanical polishing pad provided comprises a polyurethanepolishing layer containing polymeric hollow core microparticles and apolyurethane impregnated non-woven subpad. Preferably, the chemicalmechanical polishing pad provided has at least one groove on thepolishing surface.

Preferably, in the method of polishing a substrate of the presentinvention, the chemical mechanical polishing composition provided isdispensed onto a polishing surface of the chemical mechanical polishingpad provided at or near an interface between the chemical mechanicalpolishing pad and the substrate.

Preferably, in the method of polishing a substrate of the presentinvention, dynamic contact is created at the interface between thechemical mechanical polishing pad provided and the substrate with a downforce of 0.69 to 34.5 kPa normal to a surface of the substrate beingpolished.

In the method of polishing a substrate comprising silicon dioxide,silicon nitride, Ti, TiN, W or combinations thereof, polishing is doneat a platen speed of 93-113 revolutions per minute, a carrier speed of87-111 revolutions per minute, an acid chemical mechanical polishingcomposition flow rate of 125-300 mL/min, a nominal down force of 21.4kPa (3 psi) on a 200 mm polishing machine; and, wherein the chemicalmechanical polishing pad comprises a polyurethane polishing layercontaining polymeric hollow core microparticles and a polyurethaneimpregnated non-woven subpad.

The following examples are intended to illustrate the present inventionbut are not intended to limit its scope.

In the following Examples, unless otherwise indicated, conditions oftemperature and pressure are ambient temperature and standard pressure.

The polishing removal rate experiments were performed on eight-inchblanket wafers. An Applied Materials Mirra® polisher was used for allexamples. All polishing experiments were performed using a IC 1000polyurethane polishing pad with a K7+R32 groove, or VisionPad 6000™polyurethane polishing pad (commercially available from Rohm and HaasElectronic Materials CMP Inc.) with a down force of 21 kPa (3 psi), anacid chemical mechanical polishing composition flow rate of 200-300mL/min, a table rotation speed of 93 rpm and a carrier rotation speed of87 rpm. The removal rates were determined by measuring the filmthickness before and after polishing using a KLA-Tencor FX200 metrologytool.

Example 1 Chemical Mechanical Polishing Compositions

The following chemical mechanical polishing compositions are polishingslurries and were prepared by including the components and amountsdisclosed in Table 1 below. The components were combined with thebalance being deionized water. The intermediate pH was adjusted withammonia to a pH of 8 followed by adjusting the pH to 5 with succinicacid as shown in Table 2 below.

TABLE 1 Hydrogen Cerium Total BS-3¹ Peroxide DEAMS Nitrate Slurry (wt %)(wt %) (wt %) (wt %) (wt %) CS-1 100 18 — 0.075 0.01 PS-1 100 18 0.0010.075 0.01 PS-2 100 18 0.0025 0.075 0.01 PS-3 100 18 0.005 0.075 0.01PS-4 100 18 0.01 0.075 0.01 ¹FUSO BS-3 ™ nitrogen-containing colloidalsilica abrasive particles having a net positive zeta potential(available from Fuso Chemical Company, Ltd., Japan).

TABLE 2 Slurry Intermediate pH pH Titrant Final pH pH Titrant CS-1 8Ammonia 5 Succinic acid PS-1 8 Ammonia 5 Succinic acid PS-2 8 Ammonia 5Succinic acid PS-3 8 Ammonia 5 Succinic acid PS-4 8 Ammonia 5 SuccinicacidCerium oxide and cerium hydroxide compounds were coated on the silicaparticles of the present invention and stable homogeneous dispersions ofthe chemical mechanical polishing compositions of the present inventionwere formed at the final acidic pH of 5. The final colloidal silicaparticles included core silica particles comprising a nitrogen species,DEAMS, a positive zeta potential and cerium hydroxide and cerium oxidecompounds coating the silica core.

TABLE 3 Slurry ZP (mv) Appearance CS-1 N/A Gelled PS-1 14 Partialprecipitate PS-2 16 Stable dispersion PS-3 20 Stable dispersion PS-4 22Stable dispersion

Example 2

The following aqueous chemical mechanical polishing slurries wereprepared. The balance of the chemical mechanical polishing compositionswas deionized water. The initial pH titrant in each slurry was ammoniato provide an alkaline pH of 8. Following raising the pH to 8, the pH ofPS-5, CS-2, CS-3 and CS-4 were reduced to 5 with succinic acid. SlurryPS-6 was aged for 6 hours at 55° C. and the pH of the chemicalmechanical polishing composition was reduced to pH of 5 for the final pHduring heating.

TABLE 4 Hydrogen Total BS-3 peroxide DEAMS Cerium Slurry (wt %) (wt %)(wt %) (wt %) nitrate Final pH CS-2 100 1.5 — 0.0075 — 5 CS-3 100 1.5 —— 0.005 5 CS-4 100 1.5 0.002 — 0.005 5 PS-5 100 1.5 0.002 0.0075 0.005 5PS-6 100 1.5 0.002 0.0075 0.005 5Cerium oxide and cerium hydroxide were coated on the silica particles ofPS-5 and PS-6 and stable homogeneous dispersions of chemical mechanicalpolishing compositions were formed at the final acidic pH of 5. Thefinal colloidal silica particles included core silica particlescomprising a nitrogen species, DEAMS, a positive zeta potential andcerium hydroxide and cerium oxide compounds coating the silica core.

TABLE 5 TEOS RR SiN RR Polysilicon RR Slurry (Å/min) (Å/min) (Å/min)CS-2 1981 159 874 CS-3 62 134 1221 CS-4 70 157 1114 PS-5 1365 164 880PS-6 2125 244 63The chemical mechanical polishing compositions of the present invention(PS-5 and PS-6) showed enhanced TEOS removal rates over SiN andpolysilicon removal rates.

Example 3

The following chemical mechanical polishing compositions were preparedhaving the components disclosed in Table 6 below. The balance of thechemical mechanical polishing compositions was deionized water. The pHof each composition was raised to pH of 8 with ammonia. PS-7 was heattreated for 12 hours at 55° C. The pH titrant for PS-7 and CS-5 wassuccinic acid. The pH for each composition was lowered to 4.5. Ceriumoxide and cerium hydroxide were coated on the silica particles of PS-7and a stable homogeneous dispersion of a chemical mechanical polishingcomposition was formed at the final acidic pH of 4.5. The finalcolloidal silica particles included core silica particles comprising anitrogen species, DEAMS, a positive zeta potential and cerium hydroxideand cerium oxide compounds coating the silica core.

TABLE 6 Hydrogen Cerium Total BS-3 peroxide DEAMS nitrate Slurry (wt %)(wt %) (wt %) (wt %) (wt %) Final pH CS-5 100 2 — 0.01 — 4.5 PS-7 100 20.002 0.01 0.002 4.5

TABLE 7 Slurry TEOS RR SiN RR W RR Ti RR TiN RR CS-5 3191 148 55 145 265PS-7 3126 210 20 36 24

What is claimed is:
 1. A chemical mechanical polishing compositioncomprising: water; colloidal silica abrasive particles comprising asilica core comprising a nitrogen species, 0.005 wt % to 0.01 wt %cerium oxide, wherein cerium oxide coats the silica core, and a positivezeta potential; an oxidizing agent; optionally a pH adjusting agent;optionally a biocide; optionally a surfactant; and a pH less than
 7. 2.The chemical mechanical polishing composition of claim 1, wherein thesilica core of the abrasive particles further comprises an aminosilanecompound.
 3. The chemical mechanical polishing composition of claim 1,wherein the oxidizing agent is hydrogen peroxide.